Mining activity is often associated with the production of large amounts of extremely fine waste material in the form of aqueous slurry tailings. Disposal of these tailings has traditionally been to lagoons or, after dewatering, to surface heaps. Increasing environmental consideration has focused attention on disposal methods. One possible method proposed for disposing of these tailings is to use them as underground backfill for support purposes. This method requires classification and cementation in order to achieve the necessary shear strength and compression characteristics.
The addition of water absorbent polymers to mining products and process wastes for the purpose of drying the products and process wastes is known in the art, as demonstrated by United Kingdom Patent Application No. 2,200,440A and U.S. Pat. No. 4,690,971. The dried product or waste that results from the addition of a water absorbent polymer, such as, for example, cross-linked sodium polyacrylate, and the like, is brittle or in a crumbly state.
The use of water absorbent polymers with red mud wastes from a Bayer process is discussed in European Patent Application No. 0,388,108. The Application teaches the blending of a water absorbent polymer to the process waste of a Bayer process. The process waste is an aqueous liquid with dispersed solid particles. The mixture of the waste and polymer has the characteristic of easily being pumped and then becoming rigid upon standing.
The use of water absorbent polymers in aqueous dispersions from various industrial processes is also well known in the art.
Japanese Patent No. 61-212,399 discloses a composition consisting of cement, promoter and sulphates or chlorides of aluminum and iron to solidify high water content organic and inorganic waste. The composition is prepared by adding below 30 parts by weight promoter to 100 parts by weight cement. The pH is then adjusted by adding at least one sulphate or chloride of aluminum or iron in an amount below 800 parts by weight. The promoter is prepared by adding under 20 parts by weight of cement to cement mortar consisting of 100 parts by weight cement and 200 parts by weight standard sand. To prevent separation of the water and waste, water absorbent material such as polyacrylate, hydroxyethyl cellulose, methyl cellulose or bentonite, is added. The citation also teaches the addition of rust inhibitors such as an alkali salt or alkaline earth salt and the addition of water insoluble alkaline earth compounds such as sand, soil, aggregate or stone powders to the composition. The composition results in a gel with high viscosity or a hardened substance within at least three (3) hours.
Japanese Patent Application No. 1,254,292 discloses the aggregation of suspended material in water by adding a hydraulic inorganic solidifying agent and an inorganic or organic flocculant to the water. The flocculant used is Al.sub.2 (SO.sub.4).sub.3, AlCl.sub.3, sodium alginate, polyaluminum chloride, polyacrylamide, sodium polyacrylate, aminopolyacrylate or diamine diamide. The hydraulic inorganic solidifying agent is Portland cement or an aluminum cement. The solidifying agent is mixed with the flocculant in a weight ratio of 1:1-1:5. The mixture is added to the water to be treated in an amount of 5-20% based on the weight of the suspended solid.
Japanese Patent Application No. 1,139,198 discloses the reformation of earth and sand from a construction site by adding slag formed in the purification of water or sludge from the treatment process of industrial waste water, a water soluble polymer and a hydroxide, chloride, sulphate or nitrate of a cation of over two (2) valances and or hydraulic cement. The cation with over two (2) valencies is preferably an element of groups IIA, IIB, IIIA, IIIB, IVB, VB, VIB or VIIB. The hydraulic cement can be Portland cement, alumina cement, special cement, or their mixtures with fly ash or pozzolan. The water soluble polymer can be guar gum, starch, alginate, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide polyacrylate, polysaccharide or isobutylene-maleic anhydride copolymer. The polymer is added to the composition in an amount of 0.5-8 kg when the water content of the composition is 20-50%.
Soviet Union Patent Application No. 1,285,105 teaches a composition for road and runway construction which comprises 6-8 weight percent cement, 81-86 weight percent soil, 6-8 weight percent waste products from polyacrylate article production and 5-10 weight percent vat residue from vinyl chloride production.
Japanese Patent Application No. 52-090,111 discloses a method for consolidating soil comprising silt and fine sand by injecting the soil with a coagulating solution prior to treating the soil with grout. The coagulating solution can be Al.sub.2 (SO.sub.4).sub.3, NaAlO.sub.2, FeSO.sub.4, sodium salt of carboxy methylcellulose (CMC), polyacrylate, polyethyleneamine, tertiary ammonium salts, polyvinylpridines or polyacryiamides.
Japanese Patent Application No. 50-082,857 discloses a process for treating cement containing waste water which comprises adding polyacrylate and polyacrylamide to the waste water to coagulate the suspended materials. High-degree of polymerization sodium polyacrylate and nonionic polyacrylamide in a weight ratio of 1:0.5-1 are the preferred polyacrylate and polyacrylamides.
Japanese Patent No. 73-013,673 discloses a process for treating sludge from sewage and industrial processes. The process consists of filtering off or concentrating the sludge to remove water, adding greater than 3% by weight of a water hardenable cement and greater than 30 weight percent of an inorganic sulphate of sodium, iron, aluminum or ammonium. The sludge is dehydrated or concentrated by adding 15-40 weight percent Ca(OH).sub.2 as a filtration assistant and 0.05-0.2 weight percent of a water soluble organic polymer such as polyacrylamide and sodium polyacrylate.
Japanese Patent Application No. 62-089,789 discloses a process for regenerating deteriorated or cement contaminated mud. The process consists of adding a sodium salt of carboxymethylcellulose (CMC) with a degree of polymerization lower than 350.
These prior art teachings fail to suggest a composition and process for obtaining a composition that results in improved initial and long term shear strength, reduced fine loss, increased water retention, increased cement retention and reduced requirement for desliming, which eventually becomes a coherent solid.